How did it feel moving from the James Bond film "The World Is Not Enough" to "Enigma"?
"Enigma" had its own pressures. We were under-budgeted. The great thing about Bond is while it's not a blank cheque book, you do have access to a lot of facilities. If you want a Steadicam or a crane for a week, you've got them. This cost a fifth of what Bond cost. I wondered if I had learned bad habits during the Bond film. But it was fun to really be doing dialogue and scenes. It was a nice change of pace.

There is a lot of code-speak in the film. Were you ever concerned that this would alienate the audience?
A bit. It's a big challenge, this. From what Tom Stoppard first wrote, this is ABC. On the first draft, there was an explanation of the terminology on the front cover, and I couldn't understand a word of it. It's a challenge, because you don't want to dumb it down. People rightly complain how stupid most movies are, and here was a chance not to do that. I didn't want to trivialise the material, and I was making a film about brilliant people who were doing brilliant things. You can't really explain to the audience because if they understand, then the things these people are doing are not brilliant. It was a very difficult balance to strike. We tried to make it more accessible, by simplifying the code-breaking without trashing it, but also by giving it as much emotional power as possible. We built up Hester, Kate Winslet's part, who is very shadowy in the book.

Do you see it as a film about obsession?
Dougray Scott's character is totally obsessed by Claire, Saffron Burrow's character. It's a nice double-edged sword: his obsession with mathematics and his obsession with her. We were faithful to the book. The idea that he can fall in love with someone upon one meeting.

"Enigma" is released in UK cinemas on Friday 28th September